1. Field of the Invention
The present invention relates to an apparatus and a method for representative temperature measurements in same-type tubular reactors filled with solid particles, at least one tubular reactor containing a temperature measuring unit.
2. Description of the Related Art
Exothermal reactions such as oxidation reactions on an industrial scale are often, on the grounds of heat transfer and the narrow residence time distribution, carried out in tubular reactors (compare eg. U.S. Pat. No. 3,147,084, German Patent No. 11 85 590 and German Patent No. 29 03 582), the reaction volume usually being located within the tubes and the space between the tubes having a fluid heat transfer medium flowing through it for heating or cooling purposes. In general the reaction is carried out as a gas phase reaction with the aid of a heterogenous catalyst. The catalysts used are generally unsupported catalysts or support materials of identical geometrical shape and coated with active material. Such reactors are employed in the chemical industry, for example, in the production of phthalic anhydride from o-xylene or the production of acrolein or acrylic acid from propene or propane (compare eg. DE-A-1 962 431 and DE-A-2 943 707).
Any assessment of the state of the reactor, of the product quality to be expected and of the conversion ratio relies strongly on the temperature along the flow path of the reacting component in the reactor. This temperature profile is usually obtained by means of a thermocouple or a resistance thermometer. For industrial use, the thermocouple or resistance thermometer is mechanically protected against damage. To this end it is usually fitted within a thermometer protection sleeve. Such a thermometer sleeve does have the drawback, however, that it occupies a certain volume and consequently, in general, will alter the flow profile and thus the pressure drop behavior of the tube including its charge. Since, on the other hand, it is important that the temperature measurements be carried out on one or more tubular reactors which are representative of all tubular reactors, the reaction process in the tubular reactor in which the temperature is measured is required to be identical with the process in the tubular reactors without a temperature measuring unit.
It is therefore an object of the present invention to provide an apparatus and a method which allows temperatures to be measured under representative conditions in a tubular reactor.
It was found, surprisingly, that this object can be achieved if tubular reactors with and without a temperature measuring unit are set up such that the mass of the introduced solid particles is directly proportional to the free cross-sectional area of the tubular reactor in question, and the flow resistance or pressure drop and thus the mean linear velocity in the tubular reactors is identical if a gas flow rate proportional to the free cross-sectional area is passed across the tube. If these two conditions are complied with, the conditions established in the tubular reactors with and without a temperature measuring unit are comparable in reaction kinetics and thermal terms. Free cross-sectional area indicates a cross-sectional area determined in the absence of the solid particles.
It was found, surprisingly, that this object can be achieved if tubular reactors with and without a temperature measuring unit are set up such that the mass of the introduced solid particles is directly proportional to the free cross-sectional area of the tubular reactor in question, and the flow resistance or pressure drop and thus the mean linear velocity in the tubular reactors is identical if a gas flow rate proportional to the free cross-sectional area is passed across the tube. If these two conditions are complied with, the conditions established in the tubular reactors with and without a temperature measuring unit are comparable in reaction kinetics and thermal terms.
The invention therefore relates to an apparatus comprising at least two same-type tubular reactors which are filled with solid particles, at least one tubular reactor containing a temperature measuring unit, wherein tubular reactors are designed such that both the ratio of the mass of the solid particles to the free cross-sectional area of the respective tubular reactor and the pressure drop measured by an inert gas being conducted proportionately transversely to the free cross-sectional area are identical across the respective tubular reactor. Further, the invention relates to a method for treating fluid masses while generating or consuming thermal energy, in which the fluid masses are passed through a reactor apparatus comprising at least two same-type tubular reactors which are filled with solid particles, at least one tubular reactor containing a temperature measuring unit in which the temperature is measured, said method employing a reactor apparatus comprising at least two same-type tubular reactors which are filled with solid particles, at least one tubular reactor containing a temperature measuring unit, wherein tubular reactors are designed such that both the ratio of the mass of the solid particles to the free cross-sectional area of the respective tubular reactor and the pressure drop measured by an inert gas being conducted proportionately transversely to the free cross-sectional area are identical across the respective tubular reactor. The tubular reactors are designed such that both the ratio of the mass of the solid particles to the free cross-sectional area of the respective tubular reactor and the volume of reactive gas passed through per cross-sectional area are identical across the respective tubular reactor. Preferred embodiments of the invention are described in the following description, the illustrative examples, the figures and the dependent claims.